DNA aggregation induced by Mg2+ ions under different conditions

Cations-induced DNA aggregation can modify the local structure of oligonucleotides and has potential applications in medicine and biotechnology. Here, we used atomic force microscopy to investigate -DNA aggregation on Mg2+-treated glass (Mg2+/glass) and in Mg2+ solution. Atomic force microscopy topography images showed that some DNA fragments were slightly stacked together on 10mM Mg2+/glass and stacked stronger on 50mM Mg2+/glass. They also showed that DNA aggregated stronger in Mg2+ solution than on Mg2+/glass, ie, DNAs are strongly stacked and twisted at 10mM Mg2+, rolled together at 50mM Mg2+, and slightly aggregated to form small particles at 100mM Mg2+. At a specific condition, ie, heating -DNA to 92 degrees C, cooling down to 75 degrees C, adding Mg2+, and vortexing the resulting solution, DNA strongly aggregated and formed pancake-like shapes at 10 and 50mM or a large aggregate at 100mM Mg2+ solutions. Our results may be helpful for medical applications and gene therapy using cation-DNA technology.